Air inlet systems use mass air flow (MAF) sensors to determine the mass flow rate of air entering a fuel injected internal combustion (IC) engine. These MAF sensors are required to measure the flow rate and also the temperature of the air entering the engine. These data are used by the engine ECU to optimise the fuel-air mixture to maintain fuel economy and reduce emissions. Typically, these MAF sensors are mounted at the upstream inlet end of an air path from the atmosphere to the combustion chambers of an IC engine, close to the air filter.
For off-highway applications in particular, a certain (diesel) IC engine may be used in various machines and mounted in different locations. For example, an engine may be mounted forward of a cab of a backhoe loader in an inline configuration, but transversely in a side pod of a telescopic handler. As such, the ducting that provides the airpath will be different for each installation.
The present applicant has recognised that such MAF sensors currently require a dedicated calibration for each installation. Each of these calibrations costs a significant amount of money and take considerable time to produce. Each time the air path changes, a new air path calibration must be performed. In addition, the farther away that the temperature sensor is from the entry to the engine combustion chambers, the greater the potential for disparity between the measured temperature and the actual temperature of the air entering the combustion chambers, e.g. due to heat transfer from the engine.
The present invention seeks to overcome or at least mitigate the problems of the prior art.